349 



Mr. M'Culloh made some observations on the application of 

 polarized light to chemical analysis. 



After alluding briefly to the discovery of the property of circular 

 polarization in quartz, by M. Arago, and to the subsequent investiga- 

 tion, by M. Biot, of the laws of that phenomenon, as exhibited by 

 certain liquids as vvell as by quartz, Mr. M'Culloh remarked, that 

 but few analytical chemists seem to have availed themselves of the 

 advantages which circular polarization presents for the extension of 

 chemical knowledge. They appear to have considered its applica- 

 tion to practical purposes beset with laborious algebraic calculations, 

 and troublesome manipulations. And some who have only made a 

 {ew imperfect analysis by this optical method of M. Biot, have even 

 ventured to assert that simpler and quicker methods of attaining the 

 same results are very desirable ; while others have doubted the ex- 

 actness of optical analysis, rather from want of sufficient evidence or 

 information on the subject, than from any positive reason for dis- 

 belief. 



His attention had been particularly devoted to this subject, in con- 

 sequence of a very extensive series of chemical researches in relation 

 to the manufacture of sugar, and the chemical nature of the cane and 

 its various products; which researches were made by him under the 

 superintendence of Prof. A. D. Bache, and the direction of the Secre- 

 tary of the Treasury, in obedience to an act of Congress. In the 

 performance of these researches, he had also been assisted by Mr. 

 Reynolds, an able young chemist of this city. They were designed 

 to obtain information for the use of the government, and indirectly to 

 promote the sugar industry of our country. Several hundred saccha- 

 rine substances were carefully analyzed; and the processes of manu- 

 facture and refining in Cuba and the United States were fully ex- 

 amined. The practical results thus obtained, constitute the subject 

 of a report made to the Secretary of the Treasury, and by him com- 

 municated to the Senate at the close of the last session of Congress. 



Incidentally, these investigations had served to throw light upon 

 matters of a purely scientific nature; which had, therefore, been 

 omitted, as inappro[)riate in the report to Congress ; but which, for 

 that very reason, were proper subjects for the attention of this 

 Society. 



He had referred to his labours thus particularly, that he might 

 justify himself in presuming to pronounce incorrect the opinions of 

 chemists of acknowledged reputation and skill. And he thought 



VOL. IV. — 3 A 



